The couple’s son, Gabriel, was pronounced dead in hospital early on Sunday. His sister Maria remains in a critical condition today after surgery.

Mother Christinela Datcu, pictured with Das

Mihai Manea, 29, who lives on the second floor of the three-storey building, said the children lived on the top floor with their Romanian mother and Indian father.

She said: “They seemed a normal family. Das said they were eventually going to get married.”

Mr Das was arrested in Hackney at 7.15pm last night. Staff at the Pembury Hotel, where Ms Datcu works as a maid, said he quit his job there two days earlier after seven years. Ms Datcu’s best friend, who declined to be named, told the Standard she had spoken to her on the phone two hours before the attack.

Police at the scene in Finsbury Park (PA)

She said: “We spoke on Saturday night at 9pm or 9.15pm. She was saying she was fine. I know she was not fine.

“I was so shocked. Gabriel was best friends with my son. They were always playing together. “

A hammer was found in Somerfield Road near the family’s one-bed flat.

Detective Chief Inspector Dave Whellams, of the Homicide and Major Crime Command, said: “I would still like to hear from anyone who may have any information regarding this terrible incident.”

Those with information are asked to call the incident room on 020 8345 3775 or Crimestoppers on 0800 555 111.